This invention relates to apparatus for separating gas mixtures by pressure swing adsorption and relates, more particularly, to the expenditure of energy involved in moving a gas through the adsorption components of such apparatus.
Pressure swing adsorption apparatus with which this invention is concerned includes a pair of adsorbers each having a fixed bed of adsorbent material and an inlet and an outlet accommodating a flow of gas therethrough. The adsorbent material of each adsorber is adapted to fractionate at least one constituent from a gaseous mixture when the gaseous mixture is sequentially directed into the inlet of one adsorber so that the one adsorber performs adsorption while the other adsorber is simultaneously purged of adsorbed constituent with product gas withdrawn from the one adsorber and then into the inlet of the other adsorber so that the other adsorber performs adsorption while the one adsorber is simultaneously purged of adsorbed constituent with product gas withdrawn from the outlet of the other adsorber. One such pressure swing adsorption apparatus is utilized for separating nitrogen from air delivered from an air source and for providing a product stream of relatively high oxygen purity.
Pressure swing adsorption apparatus commonly employ a compressor disposed upstream of the adsorbers for moving the gaseous stream through the adsorbers, and the flow rate of the product stream exiting the apparatus is typically regulated by means of a flow metering valve situated downstream of the adsorbers. However, a reduction in the product flow rate by way of such a flow metering valve does not result in a corresponding saving of energy at the compressor. For example, whether a pressure swing adsorption apparatus which is capable of delivering a product flow rate of 5.0 SLPM is used to deliver a (full-capacity) product stream of 5.0 SLPM or whether the product flow output of the apparatus is metered to meet smaller output requirements, the power requirements of the apparatus compressor are about the same in either instance. It would be desirable to provide a pressure swing adsorption apparatus capable of operating at either a high capacity mode (for meeting higher flow rate requirements) or a low capacity mode (for meeting lower flow rate requirements) so that when in the low capacity mode, the power requirements of the compressor are reduced.
Accordingly, it is an object of the invention to provide a new and improved means enabling a pressure swing adsorption apparatus to be operated in either a high capacity mode or a low capacity mode and so that the operation of the apparatus in the low capacity mode results in a reduction in the power requirements of the apparatus compressor.
Another object of the present invention is to provide such a means wherein operation of the apparatus in the lower capacity mode reduces the sound levels of the compressor as well as the amount of heat generated by the compressor.
Still another object of the present invention is to provide such a means which facilitates the preselection of the high capacity mode of operation or the lower capacity mode of operation prior to start-up of the apparatus.
Yet another object of the present invention is to provide such a means which is well-suited for use in pressure swing adsorption apparatus used to generate an oxygen-rich product from a feed stream of air wherein such means accommodates a preselection of a high capacity or lower capacity mode of operation prior to use of the apparatus by a patient requiring oxygen therapy.
A further object of the present invention is to provide such a means which is uncomplicated in construction and effective in operation.
A still further object of the present invention is to provide a new and improved method for altering the capacity of the compressor of a pressure swing adsorption apparatus between a high capacity mode and a lower capacity, energy-saving mode.